Fuse cutout construction



Apnl 7, 1959 l R. w. THIEDE ET AL 2,881,288

Fuss: cuTouT CONSTRUCTION vFiled oct. 15. 1955 /QonczZd ZM 77u'ede UZ'ZZam H. /V'czsh IN VEN TORS.

United States Patent O 2,881,288 FUSE CUTOUT CONSTRUCTION Ronald W. Thiede, Las Cruces, N. Mex., and William H. Nash, South Milwaukee, Wis., assignors to McGraw- Edlson Company, a corporation of Delaware Application October 13, 1955, Serial No. 540,289 7 Claims. (Cl. 200--114) The present invention relates to a fuse cutout construction, and particularly relates to an improved cartridgedoor assembly adapted to be temporarily inserted in a conventional fuse cutout for determining whether a fault condition remains on a power line after interruption of the line circuit.

It is well known that to electrically close a housed fuse cutout on a line where a fault condition may exist often unnecessarily endangers the lineman servicing the fuse. Fusible elements rupturing under fault conditions develop large mechanical forces. Conventional housed cutouts are constructed with sufficient strength to counteract these expulsive forces when all of the cooperating members are in secure mechanical engagement relative to one another.

When an attempt is made to reclose conventional cutouts afer replacement of a ruptured fuse link on lines where a low impedance fault may exist, violent arcing between contacts often occurs with consequent profused evolution of hot gases. The gases are relatively confined and will act immediately to force an incompletely closed cutout door open with such violence as to injure or burn a lineman servicing the fuse.

There have been a number of devices recently developed that permit the use of temporary or permanent cartridge-door assemblies for closing the electrical circuit through the cutout after the various cooperating members have been securely engaged with one another. These devices are very adequate for operation in cases of overcurrent and for the complete protection of the lineman. This is especially true where the cartridge-door assembly was to be left in the cutout permanently.

However, a door modified to provide auxiliary circuits is relatively expensive, and since the added feature is infrequently put into use, it is not economical to be included as standard equipment. It will readily be apparent that from a purely economical standpoint it isdesirable to provide a temporary means for safely testing line circuits-one that may be adapted to be interchangeable in conventional housings, and which may be safely removed after it is determined that a fault condition no longer exists, in order that the standard relatively inexpensive cartridge-door assembly may be replaced for normal operation.

The modified improved assemblies mentioned above lend themselves readily to test purposes, but are not easily removed, even under normal line current conditions. Violent arcing between contacts and rupture of the fusible element occurs on separation of these contacts when the door is being removed, even at normal line current. To avoid this problem, the modified assemblies had to remain in place, or the line current had to be interrupted back 'of the cutout for removal of the assembly and replacement of the conventional door. The present invention provides an improved cartridge-door assembly which permits the fusible element to be interrupted in the con- 'ned arc-extinguishing chamber intended for suchinter- Y ruption in order to interrupt the electrical circuit for safe removal of the test cartridge-door assembly.

It is therefore among the objects of the present invention to provide a removable test cartridge-door assembly for housed fuse cutouts which contains in combination, an auxiliary switch means actuated by means of a conventional hook or switch stick for closing in the circuit after complete assembly of the cooperating elements of the door and cutout terminals, and in addition, contains a convenient hook stick operated assembly for releasing the fusible element to interrupt the circuit to the door for removal thereof, should fault conditions not be found to exist on the line to be tested prior to insertion of the conventional cartridge-door assembly.

An embodiment of the invention is shown in the accompanying drawing, in which the single figure is a sectional view taken longitudinally of a cutout with the improved test cartridge-door assembly being placed in position relative to the cutout terminals, and with the fuse link being shown intact, and with the circuit being completed through the auxiliary switch means as indicated in the full lines.

Referring to the drawing, it will be seen that the improved cartridge-door assembly may be embodied in conventional fuse cutouts comprising an insulating housing 1, which may be of porcelain and which is supported on a metallic bracket 2. The housing includes spaced apart stationary line terminals 3 and 4. Forming a part of the upper terminal 3 is a conventional screw-type connector 5 electrically engageable with the incoming electric line conductor 6. The upper terminal 3 also includes a resilient spring type contact 7 and a pair of U-shaped yieldable contact clips 8. v

The lower stationary terminal 4 also includes a screwtype connector 10 engageable with the outgoing line conductor 11. A pair of U-shaped contact clips 12 are also provided for this terminal for purposes hereinafter described.

Spaced apart hook-like rigid brackets 15 are provided at either side of the housing and are imbedded therein for pivotally supporting the cartridge-door. These are conventional, and have been illustrated in dotted lines tosimplify the illustration. The cartridge-door assembly, generally denoted by the reference numeral 20, comprises an insulating door 21 molded from a material such as reinforced Bakelite, and is hingedly supported on the housing 1 by means of the laterally extending pins 22 at either side thereof engageable with the hook-like brackets 15 of the housing. This arrangement permits ease in assembly and removal of the cooperating members.

The cartridge-door assembly 20 includes an insulating fuse cartridge, or tube 23, tixedly attached to the door 21 by means of the conducting contact member 24 surrounding the tube. The tube is conventionally manufactured of any hard insulating material, such as Bakelite, and including a bore liner (not specifically shown) of an arc-extinguishing material such as horn fiber, which is capable of evolving copious quantities of non-ionized gases in the presence of an electrical arc. To further secure the tube to the member 24, a straight pin 25 is driven through the contact and engages the outer peripheral wall of the tube 23. The contact member is adapted to slidably electrically engage the spring clip contacts 12 of the lower terminal 4, as shown in the drawing. The contact member is mounted on the door 21 by means of a conducting nut and bolt assembly 26 and a lower threaded screw 27. The nut and bolt assembly 26 engages a stationary auxiliary terminal 28 of an auxiliary switch mounted externally of the door. The switch also comprises the pivoted blade 29 engageable with the auxiliary terminal 28, as shown, and is pivotally attached to a lower stationary auxiliary terminal 30 by asa-1,288

means of a thru bolt and nut assembly 31. The blade 29 includes a hook stick-receiving portion 32 at its free end. The lower auxiliary terminal is secured to the door by means of conducting nut and bolt assemblies 33 engaging a contact member 35 at the lower end of the door spaced from the contact member'24. The member 35 also includes a iiip-out lever 36 pivotally attached thereto by means of a pivot pin 37, and which is biased for rotative movement in a clockwise direction, as shown, by means of a torsion spring 37. A threaded stud 40 is stakedl or otherwise assembled to the member 35. Threadingly engaging the stud is a thumb nut 41 for tightly securing a fuse link leader 42. The fuse link leader 42 protrudes from the chamber of the fuse tube 23 and passes around the flip-out lever 36 to be clamped in place by means of the thumb nut. The fuse link also includes a fusible element 43 intermediate its ends and contained within the chamber of the fuse tube. The fusible element preferably has protruding therefrom a contact portion 44 electrically engaging a conducting cap 45. The cap 45 is preferably threaded to the tube 23, and makes electrical contact with the upper spring contact 7 of the upper terminal 3 when the door is closed as shown in the drawing. The cap is formed with a laterally extending chambered portion 50 containing within its chamber a slidable plunger member 51 having secured thereto a piece of arcing material 52 engageable with the contact portion 44 of the fuse link for purposes hereinafter described. The plunger 51 is biased towards contact relationship with the portion 44 by means of a compression coil spring 53. A plunger rod S4 extends from the plunger through the .chamber to an external lever 55. The lever 55 is simply an insulating member having an indented portion 56, laterally spaced from the pivot pin 57, for engaging a hook or switch stick (not shown). The lever 55 includes a cam or rocking surface 58 for purposes hereinafter described. The conducting cap 45 includes a threaded opening at its top for receiving a set screw 60 to permit access to the interior of the fuse tube 23. The chambered portion 50 is closed by means of a threaded `cap 61 which also acts as a stop for the spring 53.

An eyelet member 65 may be made integral with the door 21 for receiving a hook stick used in mounting the door on the bracket and for removing the door from the same.

In the operation of the improved cartridge-door assembly, a conventional cartridge-door assembly (not shown) is removed from the housing 1 of the cutout after rupture of the fusible element on occurrence of an overloaded circuit, for replacement of the fuse link within its cartridge or fuse tube. After the fuse link has been reqplaced, but before replacement of the conventional door,

the lineman will often want to find out if the fault condition still remains on the line in order that the conventional door may be replaced only after normal current conditions exist thereon. That is, should an overcurrent condition still exist on the line, the lineman will be endangered when Yhe lattempts to replace conventional cartridge-door assemblies as heretofore outlined.

Therefore, the present invention contemplates the use of the improved test cartridge-door assembly as follows: The assembly 20 is provided with a modified fuse link, as shown, including the leader 42 and fusible element 43 and protruding contact portion 44. The portion 44 is inserted between the pad 52 of the plunger 51 and the internal wall of the cap 45, as shown, to provide secure electrical engagement between the fuse link and the cap 45. The link leader 42 is then wrapped around the llipout lever 36 to be secured to the `conducting stud 40 by means of the thumb nut 41.

It will be apparent, however, that the auxiliary switch means including the blade 29 is .to be maintained in open or disconnect relationship with vthe stationary auxiliary respectively. It is surface v4 terminal 28 as shown in dotted outline. This insures that the elements of the cartridge-door assembly 20 is in non-conducting relationship, and that no current will be flowing through the fuse link on closure of the door 21.

The door is placed on the hook portion of a switch stick (not shown) by means of the eyelet 65 and is pivotally suspended on the brackets 15 engaging the laterally protruding pins 22. The assembly 20 is then rocked on its pivot to the closed position shown in the draw-y ing with the contacts 7, 8 and 12-of the respective line terminals securely mechanically and electrically engaging the cartridge cap 45 and the contact member 24, again to be noted, however, that the switch blade 29 still remains in open position indicated by the dot-dash lines.

After the assembly is securely electrically and mechanically seated between the box terminals 3 and 4, the hook or switch stick (not shown) is removed from the eyelet 65 and is then engaged with the portion 32 of the auxiliary switch blade 29. The blade is then brought into circuit closing relationship with the auxiliary terminal 28, as shown in the full lines of the drawing.

lt will be apparent, that if an overcurrent condition still remains on the line, this condition will cause the fusible element 43 to melt and interrupt the ow of curr rent therethrough. The expulsion chamber of the fuse tube 23 will lthen act to extinguish any arcing, and the generated gas will aid in the expulsion of the fuse link leader 42 from the tube. The flip-out lever 36 will then be permitted to rotate in a clockwise direction to entirely remove the leader 42 from within the chamber of the fuse tube 23. The faulted line will once again be interrupted in a safe manner without endangering the servicing lineman.

On closing the auxiliary switch blade 29, if the lineman linds that the fuse does not blow, he can safely assume that no overcurrent or fault conditions remain .on the line, and that the conventional cartridge-door assembly may lbe replaced. However, as before stated, there still remains the problem of removing the test cartridge-door assembly from the box under even normal current conditions. On separation of any of the contacting electrical parts, there will be considerable arcing with consequent evolution of molten metal and other detrimental effects caused by insecure relationship between cooperating members. Therefore, the present invention provides a fuse link release mechanism for completely electrically disconnecting the cartridge-door assembly 20 prior to removing the same from the housing 1.

If it is found that no overcurrent or fault conditions remain on the line, the lineman merely engages his hook or switch stick with the portion 56 of the lever 55 and pushes upwardly to engage the cam surface 58 with the exterior of the door 21. The lever then rocksabout the 58 to withdraw the plunger rod 54 against the pressure of the coil spring 53.L Thus the plunger 51 will be released from the contact portion 44 of the fuse link to permit the.'ipout lever 36 to bear'against 'the leader 42 and withdraw the link from the interior of tletube 23. Obviously, this releasing movement will causearcing to occur. However, 'the arcing material 52 and'the horn fiber liner of the tube 23 will tend to cool any ar'cs created between the interior of the cap 45 and the contact portion 44. The arcs created will usually cause the fusible element 43 to melt thermally and sever the element portions. After the link is released and withdrawn from the tube 23, the test cartridge-door assembly 20 may be safely removed from the housing 1 and the conventional cartridge-door assembly (not shown) may be replaced in the housing.

It will `he apparent-that other devices may be substituted for the fuse link release mechanism shown herein and be within .the Iscope of the present invention. That is, it is well known that the fuse link may be mechanicalhl ruptured by means of .levers pivoted -from the lower tportion of the housing or from the cartridge and which apply a tensile pull to the fuse link to mechanically rupture the same. These latter described devices generally require relatively large levers, and have associated parts which act to decrease the flashover insulation level of a cutout and which must protrude considerably from the enclosed cutout to provide effective rotative moments for severing the fuse link portions. However, it is conceivable that such devices may be used without departing from the scope of the present invention.

It will be apparent that the present invention provides a novel safety fuse cutout assembly which may be operated to closed circuit position without endangering op erating personnel, and which may safely be opened under all current conditions for replacement of a removed conventional door assembly where a fault has previously occurred causing rupture of its fuse link.

f We claim: K

l. In a fuse cutout construction having an insulating housing including spaced apart line terminals, a cartridgedoor assembly` comprising an insulating door for enclosing said housing, an insulating fuse tube arranged to bridge said terminals on closure of said door and adapted to receive a fuse link therein, a co-nducting cap for one end of said tube electrically engageable with one of said terminals and adapted to mechanically and electrically engage said fuse link at one end thereof, manually operable means externally of said door arranged to separate said fuse link and cap to interrupt current flow from said fuse link to said cap, a first and a second contact spaced apart exteriorly of said fuse tube, the first of said contacts engageable with the other of said line terminals, auxiliary switch means interposed fbetween said contacts, and means for clamping the other end of said fuse link to the second of said spaced apart contacts.

2. In a fuse cutout construction having an insulating housing including spaced apart line terminals, a cartridgedoor assembly comprising an insulating door for enclosing said housing, an insulating fuse tube arranged to bridge said terminals on closure of said door and adapted to receive a fuse link therein, a conducting cap for one end of said tube electrically engageable with one of said terminals and including a laterally extending chambered portion, a spring biased plunger in said chambered portion normally engageable with one end of said fuse link and having a plunger rod extending externally of said door, a manually operable lever externally of said door operably associated with said plunger rod to actuate said plunger towards release of said fuse link, a first and a second contact in spaced apart relationship exteriorly of said fuse tube, the first of said contacts engageable with the other of said line terminals, auxiliary switch means interposed between said contacts exteriorly of said door, means for clamping the other end of said fuse link to the second of said spaced apart contacts and means for biasing said fuse link in a direction towards separation from engagement with said plunger.

3. In a fuse cutout construction having an insulating housing including spaced apart line terminals, a cartridgedoor assembly comprising an insulating door for enclosing said housing, an insulating fuse tube arranged to bridge said terminals on closure of said door and adapted to receive a fuse link therein, a conducting cap for one end of said tube and adapted to electrically and mechanically engage said fuse link at one end thereof, manually operable means externally of said door arranged to separate said fuse link and cap to interrupt current flow from said fuse link to said cap, a first and a second spaced apart contact exteriorly of said fuse tube, the first of said contacts engageable with the other of said line terminals and electrically connected to a one of a pair of spaced apart stationary auxiliary switch terminals exteriorly of said door, the second of said contacts including means for clamping the other end of said fuse link and means for biasing said fuse link in a directionf towards separation 'from' engagement with said cap, said second contact being electrically connected with the other of said spaced apart stationary auxiliary switch terminals, and conducting bridging means for electrically connecting said auxiliary switch terminals.

4. In a fuse cutout construction having an insulating housing including spaced apart line terminals, a cartridgedoor assembly comprising an insulating door for enclosing said housing, an insulating fuse tube arranged to bridge said terminals on closure of said door and adapted to receive a fuse link therein, a conducting cap for one end of said tube electrically engageable with one of saidl terminals and including a laterally extending chambered portion, a spring biased plunger in said chambered portion normally engageable with one end of said fuse link to retain it in contact with said cap and having a plunger rod extending externally of said door, a manually operable lever externally of said door operably associated with said plunger rod to actuate said plunger towards release of said fuse link, a first and a second contact in spaced apart relationship exteriorly of said fuse tube, the first of said contacts engageable with the other of saidv line terminals and electrically connected to a one of a pair of spaced apart stationary auxiliary switch terminals exteriorly of said door, the second of said contacts including means for clamping the other end of said fuse link and means for biasing said fuse link in a direction towards separation from engagement with said plunger and cap, said second contact being electrically connected with the other of said spaced apart stationary auxiliary switch terminals, and conducting bridging means for electrically connecting said auxiliary switch terminals.

5. In a fuse cutout construction having an insulating housing including spaced apart line terminals, a cartridgedoor assembly comprising an insulating door for enclosing said housing, an insulating fuse tube arranged to bridge said terminals on closure of said door and adapted to receive a fuse link therein, a conducting cap for one end of said tube electrically engageable with one of said terminals and including a laterally extending chambered portion, a spring biased plunger in said chambered portion normally engageable with one end of said fuse link to retain it in contact with said cap and having a plunger rod extending externally of said door, a manually operable lever externally of said door operably associated with said plunger rod to actuate said plunger towards release of said fuse link, a first and a second contact in spaced apart relationship exteriorly of said fuse tube, the first of said contacts engageable with the other of said line terminals and electrically connected to a one of a pair of spaced apart stationary auxiliary switch terminals exteriorly of said door, the second of said contacts including a thumb nut and stud for clamping the other end of said fuse link and a Hip-out lever and spring assembly for biasing said fuse link in a direction towards separation from engagement with said plunger and cap, said second contact being electrically connected with the other of said spaced apart stationary auxiliary switch terminals, and conducting bridging means for electrically connecting said auxiliary switch terminals.

6. A housed fuse cutout comprising housing means having rst and second spaced line terminals disposed interiorly thereof, a closure assembly for said housing means comprising a closure member and an insulated fuse tube containing coextensive fuse link means and disposed on one side of said closure member for electrical bridging of said first and second terminals, conducting cap means associated with one end of said fuse tube and with said first lline terminal, said cap also being mechanically and electrically engageable with said fuse link means, manually operable means disposed on said closure assembly for coaction with said fuse link means and said cap to afford mechanical and electrical disengagement therebetween, rst and second spaced contact means exterior of said fuse tube, said tirst contact means being senese in 'electrical engagement with said :second 'line terminal, said second contact meansbeingin electrical engagement with said fuse link means, and auxiliary switch means electrically interposed between s'aid irst and second co'ntact means and operable t'oelectrically vcomplete a circuit therebetween to thereby complete an electrical circuit through said cutout.

7. A housed fuse cutout comprising housing means having rst and second spaced line terminals disposed interiorly thereof, a closure assembly for said housing means comprising a closure member and an insulated fuse tube containing coextensive fuse link means and disposed on one side of said closure member for electrical bridging of said first and second terminals, conducting cap means associated with one end of said fuse tube and with said first line terminal, said cap also being mechanically and electrically engageable with said lfuse link means, first manually operable means disposed on the other side of .said closure assembly for coaction with said fuse link means and said cap to aiord mechanical and electrical disengagement therebetween, first and second spaced contact means exterior of said fuse tube, said rst contact means 'being in electrical engagement with seid second line terminal, said second Contact means being in elec trical engagement with said fuse link means, 'and second manually operable means also disposed on said other side of said closure assembly and comprising auxiliary switch means `electrically interposed between said rst and second contact means and operable to electrically complete *a circuit therebetween to thereby complete an electrical circuit through said cutout.

References Cited in the file of this patent UNTED STATES PATENTS 2,249,662 Matthews July 15, 1941' '2,269,130 Schultz Ian. 6, 1942 2,272,717 Ludwig et a1. Feb. 10, 1942 2,637,795 Hubbard May 5, 1953 2,677,738 Schneider May 4, 1954 2,716,681 Smith Aug. 30, 1955 2,734,966 Schneider Feb. 14, 1956 2,741,726 Branick et al Apr. l0, 1'95'6 2,820,867

Smith Ian. 2l, 1958 

